Whoop's Insight Into Rem Sleep: Technology Explained

The Whoop Strap Fitness Tracker is a wearable device that measures sleep based on movement and heart rate. It tracks all four stages of sleep with lab-level accuracy, including REM sleep, and will suggest optimal bedtimes based on an individual's recovery needs. The device has been validated against polysomnography, the gold standard for sleep tracking, in multiple studies, including one by the University of Arizona, which found that the Whoop had excellent accuracy compared to polysomnography. However, differentiating light sleep from sedentary wakefulness was more challenging for the device. Users have also reported mixed experiences with the accuracy of Whoop's sleep tracking, especially when it comes to distinguishing between being sedentary and being asleep.

Whoop uses heart rate and movement data to measure sleep

Whoop is a passive tracking wristband that can be used to monitor workouts, read body signals, and improve fitness regimens. It can also be used to track sleep.

The Whoop device collects hundreds of data points per second using the device's accelerometer, gyroscope, and PPG-heart rate sensor. It also measures capacitive touch and temperature, but these are not used in the sleep algorithm. PPG, or photoplethysmography, is a technique that involves measuring blood flow by assessing superficial changes in blood volume. The tiny green lights on the bottom of the Whoop device are the first part of PPG. Between the two green lights, there is a small photoreceptor that measures light. When specific colours of light are shone onto the skin, blood volume can be measured by looking at the light reflected back from the skin since blood absorbs specific colours and reflects others. Once blood flow is measured, heart rate, heart rate variability, and respiratory rate can be derived, all of which are used in the sleep detection and staging algorithms.

The Whoop device has been validated against polysomnography, the gold standard for sleep tracking, in multiple studies. In one study, Whoop overestimated total sleep time by 8.2 ± 32.9 minutes compared to polysomnography, but this difference was not significant. Another study found that Whoop had high levels of agreement with polysomnography and sensitivity to sleep (89% and 95%, respectively), and moderate specificity for wake and Cohen's kappa for chance-adjusted agreement (51% and 0.49, respectively).

Whoop measures respiratory rate, disturbances, time in bed, efficiency, light sleep, REM, and deep sleep. It also gives recommendations, telling users how much sleep they need to achieve maximum recovery.

One user reported that their Whoop device picked up 24 disturbances in one night, which was surprising to them. They also noted that their sleep efficiency stayed in the 90% range, other than a couple of dips into the 80s.

It has been validated against polysomnography, the gold standard for sleep tracking

Polysomnography is a sleep study that involves recording multiple systems in the body while a person sleeps. It is considered the gold standard for sleep tracking. It is a diagnostic test that tracks and records how multiple body systems work while the test subject is asleep. Sensors are used to monitor the activity of multiple body systems, including the heart, brain, and respiratory system, giving healthcare providers a comprehensive view of the quality of the subject's sleep.

Polysomnography can be performed at a sleep center or at home. In a sleep center, a sleep study technician will place electrodes on the subject's chin, scalp, and the outer edge of their eyelids. The subject will also have monitors to record their heart rate and breathing attached to their chest. These will remain in place while the subject sleeps. The electrodes record signals while the subject is awake (with their eyes closed) and during sleep. The test measures the amount of time it takes the subject to fall asleep and how long it takes them to enter REM sleep. A trained technician will observe the subject while they sleep and note any changes in their breathing or heart rate.

The University of Arizona conducted an independent validation of WHOOP's sleep staging analytics, which was published in the Journal of Clinical Sleep Medicine. In this study, the participants' sleep was studied using polysomnography (PSG), while they also wore WHOOP. The study showed that the accuracy of WHOOP was excellent when compared to PSG, thus demonstrating WHOOP to be a reliable, non-invasive wearable for sleep tracking. WHOOP sleep staging had high levels of agreement with polysomnography testing.

WHOOP was designed to provide the most accurate possible sleep tracking. It collects hundreds of data points per second using the device's accelerometer, gyroscope, and PPG-heart rate sensor. PPG, or photoplethysmography, is a technique that involves measuring blood flow by assessing superficial changes in blood volume. Once blood flow is measured, heart rate, heart rate variability, and respiratory rate can be derived, all of which are used in WHOOP's sleep detection and staging algorithms. WHOOP heart rate during sleep was shown to have excellent agreement with EKG, the gold standard, averaging a precision error of 1 beat per minute across 32 participants.

WHOOP accurately detects sleep duration with a precision of 17.8 minutes. It also reported highly accurate detection of REM and Slow Wave (deep) sleep. Additionally, another recent study of leading wrist-worn wearables revealed that WHOOP was the most accurate when compared to the gold-standard PSG.

Whoop measures all four stages of sleep: slow wave sleep, REM, light, and awake

The Whoop sleeping respiratory rate algorithm was shown to be within 1 breath per minute of the gold standard truth. The Whoop sleeping heart rate was shown to be within 1 beat per minute of EKG.

The Whoop device uses a 3-axis accelerometer and reflectance photoplethysmography to measure five metrics: heart rate, heart rate variability, ambient temperature, motion and movement, and skin response.

Whoop has been validated against polysomnography for detecting sleep-wake determinations with specificity and sensitivity to sleep reported at 89% and 95%, respectively.

Whoop measures sleep duration with a precision of 17.8 minutes. It also accurately detects REM and Slow Wave (deep) sleep.

It can suggest optimal bedtimes based on your body's needs

Sleep is an essential part of our lives, and getting the right amount of quality sleep is critical to our health and wellness. WHOOP is a wearable device that helps you track your sleep and improve your sleep habits. It does this by measuring your sleep across four stages: slow-wave sleep (SWS), REM sleep, light sleep, and awake time.

WHOOP's sleep tracking capabilities have been validated through independent studies, including one by the University of Arizona, which showed that WHOOP had excellent accuracy when compared to polysomnography, the gold standard of sleep tracking. WHOOP's sleeping respiratory rate algorithm was within one breath per minute of the gold standard, and its sleeping heart rate was within one beat per minute of an EKG.

One of the key features of WHOOP is its ability to suggest optimal bedtimes based on your body's needs. It does this by taking into account various factors, such as your recent sleep patterns, the strain from the day, any sleep debt you've accrued, and any naps you've taken. By understanding your unique sleep needs, WHOOP can help you optimize your sleep schedule and improve your sleep quality.

For example, if you've had a particularly strenuous day or accumulated sleep debt, WHOOP may suggest an earlier bedtime to help you get the rest you need. On the other hand, if you've had a more relaxed day and feel well-rested, WHOOP might recommend a slightly later bedtime to align with your body's natural rhythm. This dynamic approach to sleep scheduling ensures that you're getting the right amount of sleep to support your body's recovery and performance.

In addition to suggesting optimal bedtimes, WHOOP also provides daily recommendations on how to improve your sleep. It monitors your wake events, sleep efficiency, and respiratory rate to offer personalized tips on how to enhance your sleep quality. By following WHOOP's guidance, you can make gradual improvements to your sleep habits and establish a healthier sleep routine.

WHOOP also allows you to set custom haptic alarms to wake you when you're fully rested or at a specific time. This feature ensures that you're not only getting the right amount of sleep but also waking up at the optimal time for your body.

By tracking your sleep patterns over time, WHOOP helps you identify trends and make informed decisions about your sleep habits. You can view your sleep performance over a week, month, or year to spot patterns and adjust your bedtime routine accordingly. This long-term data provides valuable insights that can help you optimize your sleep schedule and make lasting improvements to your sleep hygiene.

In conclusion, WHOOP's ability to suggest optimal bedtimes based on your body's needs is a powerful tool for improving your sleep habits. By taking into account various factors and providing personalized recommendations, WHOOP helps you align your sleep schedule with your body's unique needs, supporting your overall health and wellness.

Whoop's sleep tracking is highly accurate, but it struggles to differentiate light sleep from sedentary wakefulness

Whoop is a wearable device that measures sleep based on heart rate and movement data. It has been validated in multiple studies, including one by the University of Arizona, which found that it is highly accurate when compared to polysomnography (PSG), the gold standard of sleep tracking.

Whoop tracks sleep across four stages: slow-wave sleep (SWS), REM, light, and awake. It measures hundreds of data points per second using an accelerometer, gyroscope, and PPG-heart rate sensor. It also measures capacitive touch and temperature but does not use this data in its sleep algorithm.

While Whoop has been shown to be highly accurate in detecting sleep, there are some limitations to its ability to differentiate between light sleep and sedentary wakefulness. In a Reddit discussion, a user noted that Whoop struggled to differentiate between these two states when they were sitting up in bed watching TV before sleep. This is because Whoop relies on movement and heart rate data, which can look similar in these two states.

However, Whoop has been shown to be highly accurate in detecting REM and deep sleep stages. It also provides insights into sleep duration, sleep efficiency, respiratory rate, and wake events, which can help users optimize their sleep schedules and improve sleep quality.

Overall, Whoop's sleep tracking is highly accurate, but it may struggle in certain scenarios, such as differentiating light sleep from sedentary wakefulness.

Frequently asked questions